Impact of recyclate quality and functional barrier layers on the performance of LDPE in food packaging

Summary

Low-density polyethylene (LDPE) is one of the most used polyolefins for food packaging applications. However, there are food safety concerns and challenges to recycle it back to food contact material. The present study compares the thermal, mechanical, and barrier properties, contact angle, color, and structural properties (Fourier transfer infrared) between virgin LDPE and two recycled qualities of LDPE, without and with functional barrier layers (ABA structure). In addition, migration analysis and food contact interaction study were also conducted. Thermal-induced degradation resulting from chain scission was observed in the recycled LDPE. However, the thermal behavior of the recycled films was not affected by the quality of the recyclate. On the other hand, the quality of the recyclate had a significant effect on both the mechanical and barrier properties. The tensile strength and oxygen permeability of the films were affected by the type of recyclate. The addition of LDPE as functional barrier layers in the multilayer films increased the tensile strength, while highdensity polyethylene (HDPE) did not have any additional effect on the mechanical properties. The presence of HDPE did not have any effect as a barrier layer on the permeability, irrespective of the recyclate quality. No difference in the contact angle and structure was observed between the virgin and recycled LDPE. The effect of functional barrier layers on the migration of nonvolatile compounds was not conclusive from the chromatographic analysis. The simple odor/flavor evaluation indicated that cheese in contact with the recycled LDPE without functional barrier layers resulted in higher perception of chemical/plastic flavor compared to the virgin, and the odor was apparently lower when adding LDPE as a barrier layer, while HDPE had no additional effect.